SR_TXR
if (!ISSET(sr, SR_TXR | SR_RXR))
if (ISSET(sr, SR_TXR)) {
while (bus_space_read_4(iot, ioh, IXPCOM_SR) & SR_TXR) {
while(!(bus_space_read_4(iot, ioh, IXPCOM_SR) & SR_TXR))